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From Knut Anders Hatlen <Knut.Hat...@Sun.COM>
Subject Re: [jira] Commented: (DERBY-822) Client driver: Pre-fetch data on executeQuery()
Date Sun, 12 Feb 2006 10:32:58 GMT
Kathey Marsden <kmarsdenderby@sbcglobal.net> writes:

> Knut Anders Hatlen wrote:
>>Bryan Pendleton <bpendleton@amberpoint.com> writes:
>>>>I am not convinced that the comment about LMTBLKPRC is correct, I
>>>>think it is also allowed for FIXROWPRC. Will look more into that.
>>>I think so, too, although there are a number of restrictions in the
>>>fixed row query protocol case. From page 126 of DRDA V.1:
>>>   For the fixed row query protocol, the qryrowset is a parameter on
>>>   the OPNQRY command that allows the requester to specify the return
>>>   of a rowset with the OPNQRYRM. This parameter applies only to
>>>   scrollable, non-sensitive dynamic, non-rowset cursors (QRYATTSCR
>>>   cursors, qryrowset specifies that a DRDA rowset is to be returned
>>>   with the OPNQRYRM (see Appendix B (on page 655) for more information
>>>   about DRDA rowsets). For all other cursors, the parameter is ignored
>>>   and no data is returned with the OPNQRYRM.
>>>Note that not only are there restrictions, but it also seems that
>>>the client has to request this rowset. We can't just send it
>>>automatically when the restrictions are met unless the client also
>>>sets qryrowset.
>>I think you are right, Bryan. The Query Data Transfer Protocol Rules
>>(DRDA Vol 1, p. 441) specify this in greater detail.
>>One thing that puzzles me is that the network server has no code for
>>returning QRYDTA in OPNQRYRM when the protocol is FIXROWPRC. The way I
>>read the spec, the server is required to return QRYDTA in FIXROWPRC
>>when qryrowset is non-zero (and there are no LOBs, and the cursor
>>doesn't support multi-row fetch). Does anyone know why it never sends
> Is there a case where client  sends a request with a non-zero qryrowset
> that would necessitate that the QRYDTA be sent with the OPNQRYRM?

I guess not, since we would have noticed that it failed... :)

> I am guessing at the time of implementation JCC was not sending
> qryrowset  at all and the support is not there, simply because no one
> has added it yet.  In general, there are many pieces of the  protocol
> that are missing because the existing clients don't need it and because
> the spec is biggish.  If we need it we should add it (with sensitivity
> to older clients of course).

We probably don't need it yet. I think I'll just add support for the
optional QRYDTA in the limited block protocol this time, and then
someone might add what's needed for the fixed row protocol later.

Knut Anders

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